• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.05a
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• pp.222-228
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• 1999

The two-microphone sound-intensity technique has been used for the detection of defects in radially loaded ball bearings. The difference in the sound-intensity levels measured for bearings with no defect and for those with intentionally introduced defects of different sizes in their elements under various operating conditions of loads and speeds is demonstrated. A change in the intensity frequency spectrum because of the defects is observed. The results show that the detectability of an outer-race defect is much better than that of on inner-race or ball defect. It is difficult to detect defects at lower speeds. Sound-pressure measurements were also performed fur comparison, and it is shown that the detectability of defects by sound-intensity measurements is better than that by sound-pressure measurements.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.573-574
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• 2009

• Journal of KSNVE
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• v.9 no.2
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• pp.393-400
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• 1999

Defect frequencies of rolling element bearings are experimentally investigated utilizing the two-sided directional spectra of the complex-valued vibration signals measured from the outer ring of defective bearings. The directional spectra make it possible to discern backward and forward defect frequencies. The experimental results show that the directional zoom spectrum is superior to the conventional spectrum in identification of bearing defect frequencies, in particular the inner race defect frequencies.

• Tribology and Lubricants
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• v.13 no.4
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• pp.26-32
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• 1997

The heat generation of the angular contact and the deep groove ball bearing is studied experimentally and numerically. The temperature variation of the inner and outer races and the temperature increase distribution are measured for the shaft rotational speeds, preloads, viscosities of the lubricant and lubrication methods. The measured temperature distributions are used as the input data of the numerical simulation to estimate the heat generation rate at the bearing. The temperatures of the inner and outer race increase more rapidly and approach faster to their steady values as the rotational speed increases. The optimal viscosity of the oil to minimize the heat generation is 8~10 cSt at 4$0^{\circ}C$ when the oil-air lubrication method is adopted. The heat generation of the bearing increases with the rotational speed and depends more on the lubrication method than on the preload variation.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.1
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• pp.29-36
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• 2008

In this paper, the orbital forming analysis of an automotive hub bearing was studied to predict forming performances using the explicit finite element method. To find an efficient solution technique for the orbital forming, axisymmetric finite element models and 3D solid element models were solved and numerically compared. The time scaling and mass scaling techniques were introduced to reduce the excessive computational time caused by small element size in case of the explicit finite element method. It was found from the numerical simulations on the orbital forming that the axisymmetric element models showed the similar results to the 3D solid element models in forming loads whereas the deformations at the inner race of bearing were quite different. Finally the strains at the inner race of bearing and the forming forces to the peen were measured for the same product of the numerical model by test, and were compared with the 3D solid element results. It was founded that the test results were in good agreements with the numerical ones.

• Journal of Physiology & Pathology in Korean Medicine
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• v.24 no.2
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• pp.266-271
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• 2010

Obesity occurred by energy imbalance, is increasing regardless of race, sex, age, and related to the metabolic syndrome, diabetes and cardiovascular disease. Since adipose tissue plays a critical role in regulating energy homeostasis, understanding of adipogenesis pathway and finding of regulatory mechanism for adipogenesis can be helpful to manage obesity as well as obesity-related diseases. In this study, to investigate the effects of Chestnut Inner Shell(CIS) extract on the adipogenesis in 3T3-L1 preadipocytes, 3T3-L1 preadipocytes were differentiated with adipogenic reagents for 9 days in the absence or presence of CIS extract ranging from 10 - 100 ${\mu}g/m{\ell}$. The effect of CIS extract on 3T3-L1 differentiation was examined by measuring intracelluar lipid droplet and triglyceride contents. CIS extract remarkably inhibited lipid accumulation(about 45% inhibition at 100 ${\mu}g/m{\ell}$ of CIS extract) and slightly decreased triglyceride contents(about 15% decrease at 100 ${\mu}g/m{\ell}$ of CIS extract) in 3T3-L1 preadipocytes at the concentration showing no cytotoxicity. These results demonstrated that CIS extract significantly inhibit adipogenesis and can be used for the regulation of obesity.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.211-214
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• 2006

The outer race of the constant velocity(CV) joint is an important load-supporting automotive part, which transmits torque between the transmission and the wheel. The outer race is difficult to forge, because its shape is very complex and the required dimensional tolerances are very stringent. Therefore, the internet based shape inspection system is developed in this study to provide quick and accurate data through the easy control from users. Proposed system uses mechanical displacement sensors to measure the shape of CV joint that has six inner ball grooves, and commercially available Lab-View program is used to process measured data into the dimensional shape. Developed program provides a simple user interface that enables users real-time access of data measured from industrial production lines. Furthermore, it can exchange measured data via the internet between users and forging system operators. A java applet helped the system connection via internet. A data, IP access, is transmitted to the packet by TCP/IP. Our proposed system has many advantages over current measuring systems including fast and efficient data processing by real-time control, and system flexibility.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.1
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• pp.1-8
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• 1989

A general and efficient algorithm is proposed for the analyses of multibody elastic contact problems. It is presumed that there exists negligible friction between the bodies. It utilizes a simplex type algorithm with a modified entry rule and incoporates finite element method to obtain flexibility matrices for arbitrarily shaped bodies. The multibody contact problem of a vehicle support on an elastic foundation is considered first to show the effictiveness of the suggested algorithm. Its solution is compared favorably with the existing solution. A contact problem among inner race, rollers and outer race is analyzed and the distribution of load, rigid body movements and contact pressure distributions are obtained. The trend of contact characteristics is compared with that of the idealized Hertzian solutions for two separate two-body contact problems. The numerical results obtained by directly treating a multibody contact are believed to be more exact than the Hertzian solution for the idealized two separate two-body contact problems.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.388-393
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• 2012

Vibration condition monitoring at low rotational speeds is still a challenge. Acoustic emission (AE) is the most used technique when dealing with low speed bearings. At low rotational speeds, the energy induced from surface contact between raceway and rolling elements is very weak and sometimes buried by interference frequencies. This kind of issue is difficult to solve using vibration monitoring. Therefore some researchers utilize artificial damage on inner race or outer race to simplify the case. This paper presents vibration signal analysis of low speed slewing bearings running at a low rotational speed of 15 rpm. The natural damage data from industrial practice is used. The fault frequencies of bearings are difficult to identify using a power spectrum. Therefore the relatively improved method of empirical mode decomposition (EMD), ensemble EMD (EEMD) is employed. The result is can detect the fault frequencies when the FFT fail to do it.

• Korean Journal of Applied Biomechanics
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• v.28 no.2
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• pp.93-100
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• 2018

Objective: The purpose of this study is to analyze the kinematic characteristics of the national speed skaters in the curve phase of 500-m race. Method: Seven national skaters participated in the study. Race images were acquired using a high - speed camera, and the three-dimensional motion was analyzed. Results: For skaters, whose average velocity in the curve phase is high, the velocity of entry into the straight phase was also fast. The fast skaters showed a larger maximum angle of extension of the knee joints than the relatively slow skaters, and the trunk ROM was smaller. Fast skaters tended to match the timing of the movement of the lower limb with the pelvis, while slow skaters tended to rotate the left pelvis backward. The velocity of the curve phase did not show a clear relationship with stroke time, average trunk angle, and lap time. Conclusion: It is important to skate close to the inner line, keep the trunk ROM below 10 degrees, extend the knee angle to over 160 degrees, and match the movement of the pelvis and lower limb to accelerate in the curve phase. The average velocity of the curves was fast for many athletes, but the competition rankings were low. Therefore, it is possible to improve the performance by optimizing the start technique, the running characteristics of the straight phase, and the physical factors.